Water in morning vs. evening >60F

[Discus]

I imagine if your cultural conditions preclude the growth of fungi and bacteria when you water is immaterial - as long as your plants get enough water, whenever, they're fine.

However, as most people's cultural conditions are not perfect and fungi and bacteria do sometimes take hold, altering your cultural regime ("make sure everything is dry by night") helps to mitigate that. If you have strong air circulation (be it from fans or natural wind), drying tends to happen fairly quickly no matter when you water.

Watering is perhaps the single most variable aspect of orchid culture; what works for one person may completely wreck another person's plants, so even if someone conducted a large growth trial, unless you were replicating conditions of temperature, humidity and airflow, plant species, fertiliser regime, light and medium, (and possibly other less obvious factors) following that regime (if successful) may not be all that successful in your conditions and for your motley crew of plants. Very few people would want to grow a large monoculture of a particular variety of orchid in an expensive environmentally controlled growing area.

Depending on the season, I sometimes water several times in the day, sometimes in the early evening; this is only when it is very hot and dry however. In the winter, I am cautious to water only earlier on.

Another thing to consider in winter besides disease is cold; wet leaves will undergo some degree of evaporative cooling; if your conditions are borderline "too cold" for more sensitive tropical species/hybrids, you may push them over the edge into cold damage. This is less likely during the day, as temperatures tend to be higher.

We also tend not to keep monocultures of the same plant, so even within one collection the "right" culture varies from plant to plant; when you have to cater to everyone, you usually end up catering to the most difficult or sensitive!

Experience has generally shown that "early watering" is on the whole the most effective strategy for most people. As with most things, YMMV!

[RosieC]

Completely non-scientifically I avoid watering after 12pm in the winter, but will water in the evenings during warm weather though still try and get it done in the mornings if possible.

I have sometimes had a problem with an already stressed plant getting rot after water has accidentally been left on the leaves but that can happen morning or night if it's not warm enough for it to evaporate quickly.

I've also found that a plant like Bulbophylum will rot very quickly if water is left on it. Again this can be morning or night but as water dries slower when it's cooler in the winter it's more likely at night when I keep the house cooler.

Just my unscientific observations

[james mickelso]

Terquem and Lecoufle state that erwinia and other fungal ailments in orchids are primarily transmitted plant to plant via water droplets laying on the plant at cool temps. They suggest keeping the media as dry as possible to help prevent root rot also caused by wet conditions especially at cool temps. Bertsch cautions that Botrytis, a non specific fungus, developes in water droplets left on leaves overnight. Have been reading the same for years in mags and books. Light turns on blue light receptors in guard cell membranes. This stimulates proton pumps, causing absorption of potassium ions, increasing turgor and causing stomata to open. In the light photosynthesis occurs depleting CO2 inside the leaf causing the stomata to open. Certain environmental stresses, drought, high temps, wind, that cause water depletion will lead to daytime stomata closing.

[NYCorchidman]

Orchids, and other plants, in the wild get quite wet in the early morning. those morning dews.

I think as long as there is enough air movement, plants do not get diseases.

I seldom water my plants at night, but when I do, I only pour water in the pots not spraying water on the entire plants.
I just don't want to take any chance.

[Tropic]

Here in Costa Rica, at present the rainy season begins with a daily schedule at 3 PM and lasts most of the night. This also gives us a heavy mist and lower temperatures and is expected to last until possibly November. So, this really means that the orchids here in the wild or growing outdoors are subjected to a major water dominating habitat and most of them appear to do very well. To me, this defies all my earlier conviction about early morning watering schedules that had to be faithfully followed.

[james mickelso]

But what are the temps at night where orchids grow? And how much breeze is there? A good breeze will quickly dry out the water sitting on the foliage and any temps above 65*f will inhibit most fungal problems.